775
National Geographic Photographer Willard R. Culver
Hot Coffee and Ice Cream Test a Tooth Filling's Reaction to Heat and Cold
If heat expands a filling too much, pain or breakage may result. If contracted by cold, the restoration
may loosen and fall out. Research by the Bureau has improved both filling and denture materials (page
772). The wire entering this girl's mouth leads to a thermocouple imbedded in an experimental filling to
measure temperature changes caused by hot and cold foods.
out breaking the handle, and drop it five feet
50 times on all the faces, edges, and corners.
Not long ago the Bureau invited some
master plumbers to witness a unique kind of
motion picture. As it unreeled, the audience
grew more and more excited. They were see
ing, for the first time, what actually happens
inside the plumbing system of a house.
Most plumbers thought they knew, but
didn't all agree. American cities had more
than 1,500 different plumbing codes. Bureau
men built a complete plumbing system out of
transparent plastic pipe, ran water through it,
and took movies.
These showed that many pipes were un
necessarily large, and systems often had more
traps than were needed, adding to the cost.
Today local plumbing codes are gradually
adopting these findings, saving money for the
home builder.
Brick manufacturers didn't like it at first
when the Bureau reported that an 8-inch wall
was just as safe for the average house as the
12-inch ones used for many years. But they
soon found this enabled more people to afford
to build brick houses, resulting in greater sales
of brick.
Care and Repair of the House, a book
written by Bureau men, sold nearly 140,000
copies this past year. It gives expert advice
on everything from fireproof shingles to leaky
basements and can be bought from the Gov
ernment Printing Office for 50 cents.
Rebuilding the White House
Decision to rebuild the inside of the White
House, while preserving its original outer shell,
was based on Bureau tests. Gauges put on
interior cracks showed these were growing,
while borings into the sandstone walls revealed
no damage either from the fire during the War
of 1812 or from the passage of time.
Years ago confusion reigned on American
railroads in the checking of carload weights.
A load that weighed 100,000 pounds on one
road's scale might weigh only 80,000 on
another's.
Today, in cooperation with the Association
of American Railroads, two National Bureau
of Standards test cars, equipped with stand-